This invention relates generally to braking applications of a distributed power train, and more particularly to facilitating reducing delays in braking applications of later sections of the train when communication has been lost between a remote locomotive and a lead locomotive, and to facilitate reducing undesired brake releases once a brake application has begun.
A distributed power train typically includes a lead locomotive and one or more remote locomotives, and railcars, comprehensively referred to as rolling stock. Each piece of rolling stock has braking equipment including at least a section of brake pipe, a brake control valve, reservoirs, and a brake cylinder. Each lead and remote locomotive has braking equipment that includes at least a main reservoir, a section of brake pipe, a feed valve, a cutoff valve, a relay valve, a brake control valve, and a brake cylinder. The brake pipe sections are connected to form a brake pipe that extends the length of the train. When the feed valve of a locomotive is xe2x80x9ccut-inxe2x80x9d, the relay valve is enabled, and controls the brake pipe by. charging or increasing the brake pipe pressure to release the train brakes, or exhausting the brake pipe pressure to apply the train brakes. When the feed valve is,xe2x80x9ccut-outxe2x80x9d, the relay valve is disabled and the control of the brake pipe is suspended for that locomotive. At least some known railway braking equipment does not have an accelerated emergency-braking feature wherein each piece of rolling stock in the train exhausts air from the brake pipe locally. Rather, for emergency braking situations, the entire brake pipe must be exhausted through the locomotives. During distributed power operations on trains that do not have the accelerated emergency-braking feature, emergency braking is accomplished by venting the brake pipe at both the lead and remote locomotives. However, if communication is lost between the lead and remote locomotives, then the remote locomotive will not receive the emergency brake command and the brake pipe must be entirely vented by the lead locomotive.
To further complicate such a situation, if the remote locomotive maintains the feed valve in a xe2x80x9ccut-inxe2x80x9d position, the braking equipment of the remote locomotive will attempt to increase the brake pipe pressure, thus reversing the brake application being applied from the lead locomotive. Also, if the remote locomotive remains in traction, it will continue to push the front part of the train. This situation can cause dangerously high xe2x80x9cin-trainxe2x80x9d forces to build within the train if the remote locomotive is not idled and the feed valve is not xe2x80x9ccut-outxe2x80x9d quickly enough.
To facilitate minimizing such effects, at least some known systems utilize a flow sensing feature that detects when a train brake application has been made and idles the remote locomotive and cuts-out the remote feed valve. The flow sensing features sense the airflow in the brake pipe resulting from a brake application. If the lead locomotive has communicated to the remote locomotive that a brake application is to occur, then the remote locomotive will follow the throttle and brake applications from the lead locomotive. Conversely, if the lead locomotive has not communicated to the remote locomotive that a brake application is to occur, then upon sensing a change in air flow identifying an application of the brakes, the remote locomotive attempts to communicate with the lead locomotive to verify if the brake application is desired. If the lead locomotive signals that the brake application is desired the remote locomotive will follow the throttle and brake applications from the lead locomotive. If the lead locomotive does not reply to the remote locomotive communication check, then the remote locomotive is set to idle and the feed valve is xe2x80x9ccut-outxe2x80x9d, which disables the relay valve and brake pipe charging/exhausting is suspended.
During times of communication loss between the lead and remote locomotives, the feature of verifying with the lead locomotive that brake application is desired takes a number of seconds to accomplish. During this time, the remote locomotive continues in traction and supplies air into the brake pipe, thereby minimizing the braking effect in the later sections of the train. During emergency brake applications this delayed feed valve cut-out and idling of the remote locomotive creates the undesirable situation where the front part of the train has maximum braking, the later parts of the train have minimum or no braking, and the remote locomotive continues to push the front part of the train. The net result is that the rear of the train runs into the front part of the train causing high in-train forces and possible derailment.
In one aspect, a method is provided to facilitate reducing delays in braking applications in a train using a system. The system includes at least one computer for executing brake control functions of the train and a brake pipe that extends along a length of the train for supplying air for brake operations. The train includes a lead locomotive, at least one remote locomotive, and at least one railcar. The method includes sensing a change in airflow in the brake pipe, determining whether the change in air flow is desired, sensing brake pipe pressure; and filtering undesired fluctuations in brake pipe pressure during brake applications based on the determination of whether the change in airflow is desired.
In another aspect, a system is provided to facilitate reducing delays in braking applications in a train. The system includes at least one computer for executing brake control functions of the train and a brake pipe that extends along a length of the train for supplying air for brake operations. The train includes a lead locomotive, at least one remote locomotive, and at least one railcar. The system is configured to sense a change in airflow in said brake pipe, determine whether the change in air flow is desired, sense brake pipe pressures; and filter undesired fluctuations in brake pipe pressure during brake applications based on the determination of whether the change in airflow is desired.
In yet another aspect, a system is provided for filtering undesired fluctuations in brake pipe pressure during brake application in a train. The train includes at least one of a lead locomotive, a remote locomotive, and a railcar. The system includes at least one computer for executing brake control functions of the train, and a brake pipe that extends along a length of the train for supplying air for brake operations. The brake pipe includes at least one brake pipe section such that each lead locomotive and remote locomotive in the train includes a respective brake pipe section. Each brake pipe section includes a feed valve cutoff valve and relay valve for controlling the flow of air into the respective brake pipe section, a brake pipe flow sensor for sensing air flow into the brake pipe, and a brake pipe pressure sensor for sensing pressure in the respective brake pipe section. The system is configured to initiate a feed valve cut-out for each lead locomotive feed valve and remote locomotive feed valve, measure an initial pressure in each lead locomotive brake pipe section and remote brake pipe section. The system is further configured to set a reference pressure for each brake pipe section equal to the value of the initial pressure of the respective brake pipe section.